Note: The exhibit on the museum floor uses a neon bulb like the one pictured above. Since most computer screens flicker just like the neon bulb, it can also work with your screen. How well this works will depend on the scan rate of your CRT (and how strong a bronx cheer you can make!). This will not work with LCD displays as they are too slow to strobe properly.

To Do and Notice

-Stand about ten feet away from your computer screen. Stare at the pattern above and give it a rousing raspberry. Notice that the pattern seems to wiggle.

-Vary the frequency of your raspberry and watch the screen.

-Wipe off the screen!

What's Going On?

No part of screen is moving. Instead, your whole body is vibrating, including your eyes. You can feel this vibration by putting your hand on your head as you blow. The pattern on the screen is flashing on and off 60 times a second or more. Because your body is moving, your eye is in a different position as the screen is drawn. As the image of the screen traces a path across your eye, it looks like the screen is moving. You can get this effect by blowing a raspberry while looking at any flickering display; try this in front of your television set at home


A Question

Since the Internet allows us to send our exhibits out widely, we are aware that some English expressions and idioms may not translate directly into other languages. We would like to know what you call a "bronx cheer" or "raspberry" in your language! Send us email with your translation to ronh@exploratorium.edu. (If you can give us a citation, all the better!) We'll post the results here.

English

Bronx cheer
Raspberry


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